Valve mechanism with a variable valve opening diameter

ABSTRACT

A valve mechanism with a variable valve opening cross section disposed in a passageway of an internal combustion engine and has a gas exchange valve that is acted on by the force of a valve spring and can be slid back and forth in the axial direction inside a guide by a valve control unit. Coaxial to the gas exchange valve is a seal valve acted on by the force of a coupling spring and can be slid back and forth in the axial direction by the valve control unit. The position of the seal valve in relation to the gas exchange valve in the axial direction can be changed by an adjusting unit.

The invention relates to a valve mechanism with a variable valve openingcross section with the features mentioned in the preamble to claim 1.

PRIOR ART

It is known to use internal combustion engines as the drive engine inmotor vehicles. In these engines, an air-fuel mixture is compressed andignited in a working chamber. The energy produced by this is convertedinto mechanical work. It is known to supply air and the air-fuel mixtureto the working chamber by means of valves (inlet valves) and to evacuatethe combustion products from the working chamber by means of valves(outlet valves). Controlling these valves is of considerable importancein determining the efficiency of the internal combustion engine. Inparticular, the control of the valves controls the gas exchange in theworking chamber.

In addition to a camshaft control, another known method is to use anelectrohydraulic valve control. The electrohydraulic valve controloffers the possibility of a variable or completely variable valvecontrol so that it is possible to optimize the gas exchange andconsequently to increase the motor efficiency of the internal combustionengine.

The electrohydraulic valve control includes a hydraulically actuatablecontrol valve, whose control valve piston actuates a valve body of theinlet and outlet valves and moves it toward a valve seat (valve seatring) (closing of the valve) or moves it away from the seat (opening ofthe valve). The control valve can be actuated by controlling thepressure of a hydraulic medium. The pressure control in this connectionis executed by means of solenoid valves incorporated into the hydrauliccircuit. In order to be able to achieve as optimal a gas exchange aspossible, it is desirable to achieve the highest possible switchingspeeds of the control valve. Because of these high switching speeds, thevalve body of the inlet and outlet valves strikes the valve seat ring athigh speed. On the one hand, this generates noise, and on the otherhand, the valve partners experience a relatively high degree of wear.

For example, the subject of EP 0 455 761 B1 is a hydraulic valve controldevice for an internal combustion engine. The fundamental technicalprincipal of this embodiment lies in moving an engine valve by means ofa controlled pressure of a hydraulic fluid. This embodiment includes theprovision that an electronic control unit triggers a solenoid valve,which in turn controls the movement of a reservoir piston that changesof the stroke of the engine valve.

EP 0 512 698 A1 describes an adjustable valve system for an internalcombustion engine. This embodiment is an example of a mechanical valvecontrol by means of the cams of a rotating camshaft.

The subject of U.S. Pat. No. 4,777,915 is an electromagnetic valvecontrol system for an internal combustion engine. A similar embodimentof an electromagnetic valve control is known from EP 0 471 614 A1. Inthese embodiments, the valve is moved back and forth into differentpositions through the use of electromagnetic force. The electromagnetsare disposed inside a housing part of the cylinder head, in twodifferent regions. The alternating activation of the electromagnetsmoves the valve alternatively into two end positions that respectivelycorrespond to the open position and the closed position of the valve. Inthese end positions of the valve, the opening to allow the passage ofthe air-fuel mixture into the combustion chamber is open the widest itcan go or is completely closed.

Another embodiment is known from EP 0 551 271 B1. This embodiment is avalve mechanism with a disk valve, which is disposed in a passageway ofan internal combustion engine. The fundamental principle of thisembodiment lies in dividing the valve disk in two, where the first halfof the valve disk executes only part of the stroke of the other half ofthe valve disk.

A particular disadvantage of these embodiments for valve control is thehigh cost of manufacturing and assembling the valve mechanism due to itscomplex design. This has a negative effect on the costs of manufactureand assembling. Furthermore, these embodiments require extremely highspeeds and powerful forces for valve control, resulting in an inevitableincrease in susceptibility to malfunction of the valve control due to aconsiderable wear on the parts of the valve mechanism.

ADVANTAGES OF THE INVENTION

The valve mechanism according to the invention, with the characterizingfeatures of the main claim, has the advantage over the prior art ofachieving a variable valve opening cross section through the use ofsimple means. The fact that a seal valve is disposed coaxial to the gasexchange valve, is acted on by the force of a coupling spring, and canbe slid back and forth in an axial direction by the valve control unit,wherein the position of the seal valve in relation to the gas exchangevalve in the axial direction can be adjusted by means of an adjustingunit, which is essentially comprised of a regulating valve and a workingcylinder that contains a regulating piston that can be slid by means ofa working medium, produces a valve mechanism that has a simple designand functions in a reliable, durable fashion. The advantage of theinvention is particularly comprised in that a variable valve openingcross section can be produced, wherein each individual valve can beseparately regulated. It is also possible to regulate all of the outletand inlet valves together or separately by cylinder. The variable valveopening cross section can advantageously be produced with the valvemechanism according to the invention, without producing high speeds andwithout powerful forces so that this valve mechanism has an extremelylow susceptibility to malfunction. Due to its simple design, the valvemechanism according to the invention can be inexpensively manufacturedand assembled. The invention advantageously achieves a variable valvecontrol that makes it possible to optimize the gas exchange andconsequently to increase the motor efficiency of the internal combustionengine.

A preferred embodiment of the invention provides that the valve controlunit is a camshaft.

Another preferred embodiment of the invention provides that the gasexchange valve has a rotationally symmetrical basic design and iscomprised of a valve shaft, the lower end of which has a valve disksupported on it.

Another preferred embodiment of the invention provides that the valvedisk has a conical circumference surface, which constitutes the sealingseat of the gas exchange valve.

Furthermore, a preferred embodiment of the invention provides that inthe closed position of the valve mechanism, the sealing seat of the gasexchange valve respectively rests directly against a sealing seat of theseal valve and against a valve seat ring of the cylinder head.

Another preferred embodiment of the invention provides that the sealvalve is comprised of a bushing-shaped supporting body, which isdisposed so that it can slide axially back and forth inside a guide ofthe cylinder head.

These advantageous embodiments of the invention permit the supply of theair-fuel mixture to be regulated in a highly precise manner and thusachieve a higher efficiency of the internal combustion engine.

Other advantageous embodiments of the invention ensue from the featuresdisclosed in the dependent claims.

DRAWINGS

The invention will be explained in detail below in an exemplaryembodiment in conjunction with the accompanying drawings.

FIG. 1 shows a section through a cylinder head, with the valve mechanismaccording to the invention and

FIG. 2 shows a perspective view of a seal valve of the valve mechanismaccording to the invention;

FIG. 3 shows a connection diagram of a hydraulic adjusting unit of theregulating slide valve of the valve mechanism according to the inventionand

FIG. 4 is a sectional depiction of a regulating valve of a hydraulicadjusting unit of the regulating slide valve of the valve mechanismaccording to the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

In the four Figs., the individual parts of the valve mechanism accordingto the invention are depicted schematically and are only shown with thecomponents that are essential to the invention. The same parts of thevalve mechanism according to the invention are given the same referencenumerals in the Figs. and as a rule, are only described once.

FIG. 1 shows the valve mechanism according to the invention in itsposition in the cylinder head 18 of an internal combustion engine. Thevalve mechanism has a gas exchange valve 12, which is acted on by theforce of a valve spring 16. The gas exchange valve 12 can be slid backand forth inside a guide, wherein the sliding motion is produced by avalve control unit. In a preferred embodiment of the invention, acamshaft (not shown) is provided as the valve control unit.

The gas exchange valve 12 has a rotationally symmetrical basic designand is comprised of a valve shaft 14, the lower end of which has a valvedisk 20 supported on it. FIG. 1 shows the valve mechanism in the closedposition of the gas exchange valve 12. In this position, the sealingseat 28 of the gas exchange valve 12 respectively rests directly againsta sealing seat 30 of the seal valve 10 and against a valve seat ring 22of the cylinder head 18.

The design and function of gas exchange valves 12 are generally known inand of themselves, so there is no need to discuss them in detail in thecontext of the current specification.

The invention provides that a seal valve 10 is disposed coaxial to thegas exchange valve 12. The seal valve 10 is acted on by the force of acoupling spring 24 and can be slid axially back and forth. The camshaftthat controls the sliding motion of the gas exchange valve 12 alsoproduces the sliding motion of the seal valve 10.

FIG. 2 shows a perspective view of the seal valve 10. The seal valve 10is essentially comprised of a supporting body 40 and a sealing body 38.The supporting body 40 of the seal valve 10 is bushing-shaped and iscontained so that it can slide axially back and forth inside a guide ofthe cylinder head 18. At the bottom end, the seal valve 10 is providedwith a cylindrical sealing body 38 whose outer surface constitutes thesealing seat 30. The sealing seat 38 is connected to the supporting body40 by means of connecting rods 42.

A stop disk 26 is fastened to the supporting body 40 in the vicinity ofits top end. In order to facilitate assembly, this stop disk 26 iscomprised of two parts. The two parts of the stop disk 26 areencompassed by a clamping ring 36, which holds them together.

The connection between the sealing body 38 and the supporting body 40 isdesigned so that sufficient space remains for the air or air-fuelmixture flowing through. Both for the inlet and for the outlet of air orof the air-fuel mixture, this advantageously provides for a throughopening inside the seal valve 10 large enough to permit an unhinderedflow of this medium.

FIG. 3 shows a connection diagram for a hydraulic adjusting unit with aregulating valve 44, which can be used to regulate the position of theseal valve 10 in relation to the gas exchange valve 12 by means of aregulating piston 46, which is disposed in a sliding fashion inside aworking cylinder 52. The regulating valve 44, which is embodied in theform of an intrinsically known 3-way valve, has three separate workingchambers, which permit the hydraulic fluid to flow into the workingchamber 52 and permit the hydraulic fluid to flow back out of theworking chamber 52 or completely shut off the flow of the hydraulicfluid. To this end, the sliding of the regulating valve 44 can bring theworking chambers of the regulating valve 44 into three differentswitched positions A, B, C.

FIG. 4 shows a sectional view of the design of a regulating valve 44 ofthe hydraulic adjusting unit.

The regulating valve 44 is comprised of a housing 56 with threeconnections. The connections, respectively, are a pressure connection60, a return line 54, and a cylinder connection 58. Pressure generatedby an oil pump 50 supplies the hydraulic fluid to the regulating valve44 via the pressure connection 60. The return line 54 permits thehydraulic fluid to flow from the regulating valve 44 to the oil tank 48(not shown here). The cylinder connection 58 communicates with theworking cylinder 52 of the adjusting unit and is used to supply thehydraulic fluid to the working cylinder 52 and to drain hydraulic fluidfrom the working cylinder 52. The cylinder connection 58 is disposed onthe one side of the regulating valve 44, approximately in its middle.The pressure connection 60 and the return line 56 are disposed onopposite sides of the regulating valve 44, close to its respectiveupstream and downstream ends.

An adjusting pin 90 is supported so that it can be slid axially in thehousing 88 of the regulating valve 44. The adjusting pin 90 is connectedat one of its ends to a stroke drive unit 84, which generates an axialsliding motion of the adjusting pin 90. The adjusting pin 90 iscontinuously acted on by the force of a spring 78, which presses a stopconnected to the adjusting pin 90 against a support 86 of the housing 88of the regulating valve 44. At the opposite end of the adjusting pin 90,it is supported so that it can slide in a bore of a sealing seat support72 of the housing 88 of the regulating valve 44.

A first driver disk 64 and a second driver disk 66 are fastened to theadjusting pin 90 spaced apart from each other. The first driver disk 64serves to support a first seal valve 68 and the second driver disk 66serves to support a second seal valve 70, wherein both of the sealvalves 68, 70 are supported so that they can slide axially on theadjusting pin 90 and a compression spring 80 is disposed between the twoseal valves 68, 70, whose force presses the seal valves 68, 70 intocontact with their respective associated driver disks 64, 66. The firstseal valve 68 has a conical outer surface, which corresponds to asealing seat 74 of the housing 88 of the regulating valve 44. The secondseal valve 70 also has a conical outer surface, which corresponds to asealing seat 76 of the sealing seat support 72 of the regulating valve44.

The valve mechanism shown in FIGS. 1 and 2 functions in the followingmanner:

The valve control unit, which is a camshaft (not shown) in a preferredembodiment of the invention, can either open or close the gas exchangevalve 12. As in a conventional valve gear mechanism, the camshaft pushesdown the valve shaft 14 of the gas exchange valve 12 and thus controlsthe course of movement of the gas exchange valve 12. In this connection,all known methods can be used, which are based on the technicalprinciples of a bucket tappet, a tilting lever, a drag lever, and thelike.

The camshaft 44 works against the restoring force of the valve spring16, which is supported against the cylinder head 18 and against thevalve disk 20 that moves along with the gas exchange valve 12. Therotation of the camshaft 44 pushes the gas exchange valve 12 downward,and the sealing seat 28 of the gas exchange valve 12 lifts up from thevalve seat ring 22.

The coupling spring 24, which is subjected to a certain degree ofinitial stress, causes the seal valve 10 to move along with it. Thecoupling spring 24 is supported against the valve disk 20 and the stopdisk 26, which is connected to the seal valve 10. As a result, thesealing seat 28 of the seal valve 10 is pressed against the sealing seat28 of the gas exchange valve 12. Since an annular gap seal is providedbetween the sealing body 38 and the valve seat ring 22, only a veryslight air quantity (leakage) can travel into the combustion chamber 32.

The gas exchange valve 12 and therefore also the seal valve 10 followthe course of the cam until the stop disk 26 comes into contact with theregulating slide valve 34.

In its starting position, the regulating slide valve 34 can be adjustedin relation to the gas exchange valve 12 in the axial direction of thevalve shaft 14. The regulating slide valve 34 here can only be adjustedby means of a corresponding adjusting unit, a preferred embodiment ofwhich, in the form of a hydraulic adjusting unit, is shown in detail inFIGS. 3 and 4. Otherwise, the position of the regulating slide valve 34inside the valve mechanism remains fixed, even when external forces acton it. There is also the possibility of embodying the adjusting unit inan electric or pneumatic form.

As soon as the stop disk 26 comes into contact with the regulating slidevalve 34, then the seal valve 10 can execute no further movement in theopening direction of the gas exchange valve 12. Since the camshaft movesthe gas exchange valve 12 further, the sealing seat 28 of the gasexchange valve 12 lifts up from the sealing seat 30 of the seal valve10, which allows air to travel into the combustion chamber 32. Thecoupling spring 24 is compressed in the process of this.

If the gas exchange valve 12 is following the closing flank of thecamshaft, then the valve spring 16 pushes the gas exchange valve 12 inthe closing direction. The sealing seat 28 of the gas exchange valve 12comes to rest against the sealing seat 30 of the seal valve 10. The sealvalve 10 is carried along with the gas exchange valve until the sealingseat 28 of the gas exchange valve 12 comes to rest against the valveseat ring 22 and the gas exchange valve 12 is closed.

The gas exchange valve 12 and consequently also the seal valve 10 followthe course of the cam on the camshaft 44. At a particular moment, thestop disk 26 that is connected to the seal valve 10 comes into contactwith the regulating slide valve 34 (state shown in FIG. 1). Then theseal valve 10 can no longer follow the course of the cam on the camshaft44. The gas exchange valve 12 lifts up from the seal valve 10 and aircan travel into the combustion chamber.

Axial shifting of the position of the regulating slide valve 34 by meansof an adjusting unit can be used to set when the sealing seat 28 of thegas exchange valve 12 lifts up from the sealing seat 30 of the sealvalve 10. This advantageously makes it possible to regulate the openingcross section of the gas exchange valve 12 and consequently also thequantity of the air traveling into the combustion chamber 32.

The hydraulic adjusting unit of the seal valve 10, which is shown in theform of a connection diagram in FIG. 3, functions as follows:

The regulating piston 46 is connected to the regulating slide valve 34and, like it, can slide in the axial direction of the valve shaft 14 ofthe gas exchange valve 12. The sliding is executed with the aid of ahydraulic fluid, which travels under a particular pressure into theworking cylinder 52 of the adjusting unit in which the regulating piston46 is contained in a sliding fashion.

If the regulating valve 44 is in the third switched position C, thenhydraulic fluid travels into the working cylinder 52 of the adjustingunit. An oil pump 50 supplies the hydraulic fluid through the supplyline 54 and into the working cylinder 52. The regulating piston 46 movesupward in the axial direction of the valve shaft 14. This results in thefact that the stop disk 26 (FIG. 1) comes into contact with theregulating slide valve 34 earlier. The seal valve 10 therefore executesa shorter motion so that the valve opening cross section is increased.

FIG. 3 shows the regulating valve 44 of the adjusting unit in the firstswitched position A. In this first switched position A of the regulatingvalve 44, hydraulic fluid can travel out of the working cylinder 52 viathe return line 56 into the oil tank 48. If the contact disk 26 restsagainst the regulating slide valve 34, then the prestressing force ofthe coupling spring 24 acts on the regulating slide valve 34 and pressesit downward as long as the regulating valve 44, is in the first switchedposition A. It is also possible to provide an additional spring betweenthe valve disk 20 and the regulating slide valve 34, which exerts apermanent prestressing force on the regulating slide valve 34. Since theregulating slide valve 34 is now in a lower position, in the nextactuation by the camshaft, the stop disk 26 comes into contact with theregulating slide valve 34 at a later point in time. The seal valve 10thus executes a longer movement so that the valve opening cross sectionis reduced.

If the regulating valve 44 is disposed in the second switched positionB, then the flow of the hydraulic fluid through the working chamber isstopped in both directions. As a result, no hydraulic fluid can flowinto the working cylinder 52 and also, no hydraulic fluid can flow outof the working cylinder 52. The position of the regulating piston 46therefore remains constant.

A preferred embodiment of the invention provides that the regulatingvalve 44 can be electrically triggered. In this case, the regulatingvalve 44 is designed so that it is always in the first switched positionA without a being supplied with current. This results in the fact thatwhen the regulating valve 44 is without current, the regulating piston46 is pressed downward and consequently sets the opening cross sectionof the gas exchange valve 12 to the minimal possible value.

The regulating valve 44 of the adjusting unit of the seal valve 10 shownin FIG. 4 functions as follows:

The hydraulic fluid travels via the pressure connection 60 into thehousing 88 of the regulating valve 44. The prestressing force of thespring 78 presses the stop 82 connected to the adjusting pin 90 againstthe support 86 of the housing 88. The first driver disk 64 lifts thefirst seal valve 68, which is movably supported on the adjusting pin 90,up from the sealing seat 74 of the housing 88. At the same time, thespring 88 presses the second seal valve 70 against the sealing seat 76of the sealing seat support 72 of the regulating valve 44.

The fluid can travel from the working cylinder 52 of the adjusting unit,through the cylinder connection 62, and into the return line 56. At thesame time, the connection between the pressure connection 60 and thecylinder connection 62 is closed. This corresponds to the first switchedposition A according to FIG. 3.

The stroke drive unit 84, whose design is known per se to one skilled inthe art and is therefore not shown in detail, can exert a force on theadjusting pin 90 in the axial direction.

The exertion of a particular force of the stroke drive unit 84 on theadjusting pin 90 causes the adjusting pin 90 to move in the axialdirection. The force of the stroke drive unit 84 that must be exerted inorder to bring about this movement depends respectively on theprestressing forces of the spring 78 and the compression spring 80against which the stroke drive unit 84 must work. The switched positionB of the regulating valve 44 (FIG. 3) is achieved by selecting the driveforce of the stroke drive unit 84 so that the adjusting pin 90 movesuntil the compression spring 80 presses the first seal valve 68 againstthe first sealing seat 74. In this case, the second driver disk 66 hasnot yet lifted the second seal valve 70 up from the sealing seat 76 ofthe sealing seat support 72. In this switched position B of theregulating valve 44, the two connections are closed so that no hydraulicfluid can flow.

In order to reach the switched position C of the regulating valve 44according to FIG. 3, the force that the stroke drive unit 84 exerts onthe adjusting pin 90 must be increased. The second driver disk 66 liftsthe second seal valve 70 up from the sealing seat of the sealing seatsupport 72. In this switched position C of the regulating valve 44,hydraulic fluid can travel from the pressure connection 60 into thecylinder connection 62.

In order to achieve the switched positions A, B, and C according to FIG.3 of the regulating valve 44, it is necessary that the spring forces ofthe spring 78 and the compression spring 80 as well as the force to beexerted by the stroke drive unit 84 to be precisely matched to oneanother.

The invention advantageously makes it possible to regulate the openingcross sections of the gas exchange valves 12 of an internal combustionengine either individually or in groups through the use of one adjustingunit. As a result, the embodiment according to the invention isparticularly inexpensive.

1-24. (canceled)
 25. In a valve mechanism with a variable valve openingcross section, wherein the valve mechanism is disposed in a passagewayof an internal combustion engine and has a gas exchange valve that isacted on by the force of a valve spring and can be slid back and forthin the axial direction inside a guide by a valve control unit, theimprovement comprising, a seal valve (10) coaxial to the gas exchangevalve (12), acting on the seal valve (10), the seal valve being axiallyslidable back and forth by the valve control unit, an adjusting unitoperable to change the position of the seal valve (10) in relation tothe gas exchange valve (12) in the axial direction, the adjusting unitbeing essentially comprised of a regulating valve (44) and a workingcylinder (52) that contains a regulating piston (46) that can be slid bymeans of a working medium.
 26. The valve mechanism according to claim25, wherein the valve control unit is a camshaft.
 27. The valvemechanism according to claim 25, wherein the gas exchange valve (12) hasa rotationally symmetrical basic design and is comprised of a valveshaft (14), the upper end of which has a valve disk (20) supported onit.
 28. The valve mechanism according to claim 27, wherein the valvedisk (20) has a conical circumference surface, which constitutes thesealing seat (28) of the gas exchange valve (12).
 29. The valvemechanism according to claim 25, wherein, in the closed position of thevalve mechanism, the sealing seat (28) of the gas exchange valve (12)respectively rests directly against a sealing seat (30) of the sealvalve (10) and against a valve seat ring (22) of the cylinder head (18).30. The valve mechanism according to claim 25, wherein the seal valve(10) comprises of a bushing-shaped supporting body (40), which issupported so that it can slide axially back and forth inside a guide ofthe cylinder head (18).
 31. The valve mechanism according to claim 25,wherein the seal valve (10) comprises a bushing-shaped supporting body(40) constituting the guide of the gas exchange valve (12), inside ofwhich guide the gas exchange valve (12) can slide back and forth in theaxial direction.
 32. The valve mechanism according to claim 25, wherein,at its bottom end, the seal valve (10) has a cylindrical sealing body(38) whose outer surface constitutes the sealing seat (30).
 33. Thevalve mechanism according to claim 25, wherein the seal valve (10)comprises a supporting body (40), and wherein the sealing body (38) isconnected to the supporting body (40) by means of connecting rods (42).34. The valve mechanism according to claim 25, wherein the seal valve(10) comprises a support body, and a stop disk (26) fastened to thesupporting body (40) of the seal valve, close to its top end.
 35. Thevalve mechanism according to claim 34, wherein the stop disk (26) iscomprised of two parts.
 36. The valve mechanism according to claim 35,wherein the two parts of the stop disk (26) are encompassed by aclamping ring (36).
 37. The valve mechanism according to claim 25,wherein the working medium of the adjusting unit is a hydraulic fluid.38. The valve mechanism according to claim 25, wherein the regulatingvalve (44) is electrically triggered.
 39. The valve mechanism accordingto claim 25, wherein the working medium of the adjusting unit is ahydraulic fluid, wherein the regulating valve (44) is electricallytriggered, the regulating valve (44) being operable to produce threedifferent switched positions (A, B, C), of which the first switchedposition (A) opens the return flow of hydraulic fluid and the thirdswitched position (C) opens the inflow of hydraulic fluid, while thesecond switched position (B) shuts off the flow of the hydraulic fluid.40. The valve mechanism according to claim 39, wherein the regulatingvalve (44) can trigger a working cylinder (52), which contains theregulating piston (46) in a sliding fashion, wherein the regulatingpiston (46) is connected to the regulating slide valve (34) of the valvemechanism.
 41. The valve mechanism according to claim 40, wherein theregulating valve (44) is essentially comprised of a housing (88) thathas a central working chamber (92) with three connections, wherein anadjusting pin (90) that can slide axially is disposed inside the workingchamber (92).
 42. The valve mechanism according to claim 41, wherein thethree connections of the central working chamber, respectively, are apressure connection (60), a return line (56), and a cylinder connection(58).
 43. The valve mechanism according to claim 42, wherein thepressure connection (60) is connected to an oil pump (50), the returnline (56) is connected to an oil tank (48), and the cylinder connection(58) is connected to a working cylinder (52) of the adjusting unit. 44.The valve mechanism according to claim 43, wherein the adjusting pin(90) is acted on by the force of a spring (78) and is connected to astroke drive unit (84).
 45. The valve mechanism according to claim 44,wherein further comprising a first driver disk (64) and a second driverdisk (66) fastened to the adjusting pin (90) spaced apart from eachother and serve to support a first seal valve (68) and a second sealvalve (70), wherein both of the seal valves (68, 70) are supported onthe adjusting pin (90) in an axially sliding fashion and a compressionspring (80) is disposed between the two seal valves (68, 70), whoseforce can bring the seal valves (68, 70) into contact with theirrespective associated driver disks (64, 66).
 46. The valve mechanismaccording to claim 45, wherein the first seal valve (68) has a conicalouter surface, which corresponds to a sealing seat (74) of the housing(88), and the second seal valve (70) has a conical outer surface, whichcorresponds to a sealing seat (76) of the sealing seat support (72) ofthe regulating valve (44).
 47. The valve mechanism according to claim45, wherein characterized in that the through openings of the workingchamber (92) to the return line (56) and/or to the pressure connection(50) can be closed depending on the axial position of the adjusting pin(90).
 48. The valve mechanism according to claim 25, wherein the motoroil that is present can be used as the hydraulic fluid of the adjustingunit.